Question about Basics of Gravity

[tylers100]

- Question

"Gravity is the weakest of the four fundamental interactions of physics, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a consequence, it has no significant influence at the level of subatomic particles.[4] In contrast, it is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape and trajectory (orbit) of astronomical bodies."
link: https://en.wikipedia.org/wiki/Gravity

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

[studiot]

7 hours ago, tylers100 said:

- Question

"Gravity is the weakest of the four fundamental interactions of physics, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a consequence, it has no significant influence at the level of subatomic particles.[4] In contrast, it is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape and trajectory (orbit) of astronomical bodies."
link: https://en.wikipedia.org/wiki/Gravity

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

Which force predominates depends upon the distance the interaction operates.

That is often stated at bit more vaguely as the scale.

 

When considered as 'forces' the scale or distance order ( not strength order)  is weak < strong < electromagnetic < gravity.

 

So

the weak force predominates at the very shortest scales, smaller than nuclear particles,

The strong force predominates at scales the size of the nucleus

The electromagnetic force predominates at scales the size of a molecule (ie bigger than an atom)

The gravitational force predominatres at the size of galaxies.

This Wiki article has readable presentations of all this and more.

Note the key word is interactions, not forces

https://en.wikipedia.org/wiki/Fundamental_interaction

 

At scales the size of the nucleus and smaller

[swansont]

9 hours ago, tylers100 said:

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

Yes. Each particle in some collection attracts in proportion to its mass, and the total force is the sum of these individual forces. It’s always attractive, so there is no cancellation 

[tylers100]

@studiot and @swansont, thanks for replying.

I understand a bit better about the distance of interactions, but after reading some on fundamental interaction wiki page.. I'm a bit overwhelmed by it at this moment, but one thing caught my attention, this snippet of paragraph on the fundamental interaction wiki page:

"An even bigger challenge is to find a way to quantize the gravitational field, resulting in a theory of quantum gravity (QG) which would unite gravity in a common theoretical framework with the other three forces. Some theories, notably string theory, seek both QG and GUT within one framework, unifying all four fundamental interactions along with mass generation within a theory of everything (ToE)."
link: https://en.wikipedia.org/wiki/Fundamental_interaction

Quantize = Requires an understanding of quantum mechanics in order to quantize gravity (transition from classical to QM) , but I do not fully understand QM (e.g. mathematics).

Still, I feel a drawing or pulling to the gravity topic as part of science subject. I feel like jumping to it.

[studiot]

53 minutes ago, tylers100 said:

@studiot and @swansont, thanks for replying.

I understand a bit better about the distance of interactions, but after reading some on fundamental interaction wiki page.. I'm a bit overwhelmed by it at this moment, but one thing caught my attention, this snippet of paragraph on the fundamental interaction wiki page:

"An even bigger challenge is to find a way to quantize the gravitational field, resulting in a theory of quantum gravity (QG) which would unite gravity in a common theoretical framework with the other three forces. Some theories, notably string theory, seek both QG and GUT within one framework, unifying all four fundamental interactions along with mass generation within a theory of everything (ToE)."
link: https://en.wikipedia.org/wiki/Fundamental_interaction

Quantize = Requires an understanding of quantum mechanics in order to quantize gravity (transition from classical to QM) , but I do not fully understand QM (e.g. mathematics).

Still, I feel a drawing or pulling to the gravity topic as part of science subject. I feel like jumping to it.

Perhaps I should have noted before that the Wiki article refers to other models/explanations of force -  the article is fairly comprehensive.

That is why I said 'force' and why I referred to 'interactions'.

I suggest you get a good hold on the simple everday idea of force before looking at, for instance, the exchange particle model.

Remember they are all models, none are perfect.

[tylers100]

On 10/17/2021 at 12:33 PM, studiot said:

Perhaps I should have noted before that the Wiki article refers to other models/explanations of force -  the article is fairly comprehensive.

That is why I said 'force' and why I referred to 'interactions'.

I suggest you get a good hold on the simple everday idea of force before looking at, for instance, the exchange particle model.

Remember they are all models, none are perfect.

Yep. Except the fact that this thread is focused specifically on the basics of gravity. You interjected into and jumped to some forces or other interactions, leading me to re-shift my focus to these which is not what I originally intended.

 

[studiot]

17 minutes ago, tylers100 said:

Yep. Except the fact that this thread is focused specifically on the basics of gravity. You interjected into and jumped to some forces or other interactions, leading me to re-shift my focus to these which is not what I originally intended.

 

This might help

[Markus Hanke]

On 10/17/2021 at 11:27 AM, tylers100 said:

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

Mass is what usually comes to mind first - but it’s important to realise that other forms of energy also have gravitational effects. Examples are pressure, stresses and strains within materials; electromagnetic fields; and even the gravitational field itself acts (at least in some sense) as its own source. Hence, gravity is a lot richer and more complicated than the simplified picture most of us are taught in school.

[Intoscience]

1 hour ago, Markus Hanke said:

Mass is what usually comes to mind first - but it’s important to realise that other forms of energy also have gravitational effects. Examples are pressure, stresses and strains within materials; electromagnetic fields; and even the gravitational field itself acts (at least in some sense) as its own source. Hence, gravity is a lot richer and more complicated than the simplified picture most of us are taught in school.

Would you say that this is the reason why gravity is modelled in 2 ways - spacetime warping and/or particle exchange?

[swansont]

45 minutes ago, Intoscience said:

Would you say that this is the reason why gravity is modelled in 2 ways - spacetime warping and/or particle exchange?

It's three, really - gravitational field, warping, and particle exchange. 

The former two are classical, that latter is quantum, and in that regard this is no different than electromagnetism having classical and quantum models.  

[Intoscience]

6 minutes ago, swansont said:

It's three, really - gravitational field, warping, and particle exchange. 

The former two are classical, that latter is quantum, and in that regard this is no different than electromagnetism having classical and quantum models.  

Ok, thanks

[MigL]

On 10/25/2021 at 7:06 AM, Intoscience said:

On 10/25/2021 at 5:38 AM, Markus Hanke said:

Mass is what usually comes to mind first - but it’s important to realise that other forms of energy also have gravitational effects. Examples are pressure, stresses and strains within materials; electromagnetic fields; and even the gravitational field itself acts (at least in some sense) as its own source. Hence, gravity is a lot richer and more complicated than the simplified picture most of us are taught in school.

Would you say that this is the reason why gravity is modelled in 2 ways - spacetime warping and/or particle exchange?

No, but it is the reason gravity is not renormalizable and can't be easily persuaded to play well with Quantum Field theory.

[tylers100]

Visualization

At this moment I could picture gravity almost similar to torus field although is more 3D torus filling in almost 3d radial from centre.

Similar to electromagnetism. Just like solar flares going back to the Sun. I wonder if gravity in the Sun govern that? Or could solar flares' appearance "give" off gravity's "visual" version of interactions?

quote: "Gravity not only pulls on mass but also on light. Albert Einstein discovered this principle. If you shine a flashlight upwards, the light will grow imperceptibly redder as gravity pulls it. You can't see the change with your eyes, but scientists can measure it."

from link: https://spaceplace.nasa.gov/what-is-gravity/en/

Google "solar flares, sun"

[swansont]

3 hours ago, tylers100 said:

Visualization

At this moment I could picture gravity almost similar to torus field although is more 3D torus filling in almost 3d radial from centre.

Similar to electromagnetism. Just like solar flares going back to the Sun. I wonder if gravity in the Sun govern that? Or could solar flares' appearance "give" off gravity's "visual" version of interactions?

quote: "Gravity not only pulls on mass but also on light. Albert Einstein discovered this principle. If you shine a flashlight upwards, the light will grow imperceptibly redder as gravity pulls it. You can't see the change with your eyes, but scientists can measure it."

from link: https://spaceplace.nasa.gov/what-is-gravity/en/

Google "solar flares, sun"

The image of a solar flare going back to the sun show matter traveling that path, not light. The matter emits or scatters light into your eye (or the camera’s lens)

But yes, gravity would be involved, along with the sun’s magnetic field.

[tylers100]

Context

This Earth's gravity (or planetary gravity).

Dimensions

While I was diagramming at earlier times, I noticed something to do with directions in each of different dimensions. More room to move around in 2D and 3D, but 1D on other hand, only can go or back in one direction. When I think of visibly effects by gravity (e.g. mass things go down to it until equilibrium, massless things go away from it), following the pattern is like go or back in one direction governs by 1D.

But since the gravitational field from this Earth goes nearly, assuming that it is true, omni-directional sphere, then that involves all dimensions as nearly anywhere (following the requirement of gravity's range, infinite range if true). This seem to imply gravity could be 4D in nature whereas its produced effects are 1D-3D.

[Note: 4D for this post by myself with my point of viewpoint / perspective, means Fourth Dimension as in space-time continuum or covering nearly all points in space-area (e.g. perception would be like able to see or touch all points at once while within 4D. An analogy; Rubik's cube, while all squares move in 3D, 2D, and 1D the backbone of the cube is 4D. Conceptually speaking.]

Is there any evidence that gravity is 4D?

 

[Bufofrog]

4 minutes ago, tylers100 said:

Is there any evidence that gravity is 4D?

Yes, evidence points to gravity being 4D and it's produced effects are 4D.  3 spatial and 1 temporal dimension.

[tylers100]

14 minutes ago, Bufofrog said:

Yes, evidence points to gravity being 4D and it's produced effects are 4D.  3 spatial and 1 temporal dimension.

Ok, thanks.

Honestly, I'm a bit unsure what to think and ask next to go in regard to the gravity thing now. I'm was trying to tackle what make gravity (especially this Earth) tick, so maybe I could can contribute to further an understanding about the gravity, in order to see if more practical innovation is possible without having to use fuel (e.g. artificial gravity for spaceflight, artificial anti-gravity for launching spaceships) but these at this moment seem to be impossible.

[Bufofrog]

2 hours ago, tylers100 said:

(e.g. artificial gravity for spaceflight, artificial anti-gravity for launching spaceships) but these at this moment seem to be impossible.

There are ways to simulate gravity in space but there is nothing like antigravity.

[MigL]

On 10/17/2021 at 12:27 AM, tylers100 said:

Gravity is the weakest of the four fundamental interactions of physics, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction.

Didn't notice this when you first posted a couple of years back, but that 1038 times is actually 10³⁸, or 38 orders of magnitude weaker.
Same goes for the other numbers posted.

Keep in mind that this is at atomic particle scale; if you compare at scales approximately 10 times the mass of our sun, you will find that gravity is the strongest and no other interactions can resist gravitational collapse to a Black Hole
As Studiot mentions in the first answer, scale matters.

4 hours ago, tylers100 said:

Is there any evidence that gravity is 4D?

A lot of the differences between Newtonian gravity and GR are due to temporal curvature.
The anomalous orbit of Mercury, in the strong gravity field of the Sun, is mostly due to temporal curvature..

[mistermack]

What do posters think the mechanism of gravity is? I instinctively can't get my head around it being down to a particle, because of the distances involved. As I understand it (which is sure to be wrong) every massive object interacts with every other, through gravity. Which seems to require that every proton, neutron and all the rest are constantly emitting enough particles to constantly interact with every other particle in the Universe. How many particles does a proton emit per second, to interact constantly with every other massive particle in the Universe? And how much energy would that require, and where does it come from? 

For the other forces, acting over tiny distances it seems to be feasible, but gravity over billions of light years, in all diractions ? It's just mind boggling. (to me)

 I must be fundamentally getting it wrong somewhere, but please don't put me right with maths, it goes in through one ear, and straight out of the other. 🤪

[Mordred]

It's more accurate to think of gravity as spacetime curvature. In order to understand how mass affects spacetime curvature you need a few details.

1) Mass is resistance to inertia change or acceleration.

2) spacetime curvature doesn't describe a shape per se, it describes the geodesic paths that particles will follow. If two light beams stay parallel spacetime is flat. If they converge you have positive curvature. If they diverge you have negative curvature

3) All particles and their respective fields contribute to the mass term as well as the curvature. Higgs, EM, strong and weak force included. Subjective to their respective range for each force.

An everyday example that may help understand the above. A electronic conductor sending signals past an EM field may experience signal propagation delay as a result of its orientation to that field. This phenomena has remarkable similarities to how spacetime curvature affects other particles and their interactions. Also helps better understand time dilation.

 

 

Edited May 8, 2023 by Mordred

[mistermack]

6 minutes ago, Mordred said:

It's more accurate to think of gravity as spacetime curvature.

I get that, but that's describing the results of gravity, rather than explaining the mechanism. 

[Genady]

32 minutes ago, mistermack said:

every massive object interacts with every other, through gravity

Yes, but not only. Massless particles are affected by gravity too. They also produce gravity through pressure. Also, massive particles produce gravity not only by their mass but also by pressure and stress, if these are present.

 

36 minutes ago, mistermack said:

How many particles does a proton emit per second, to interact constantly with every other massive particle in the Universe? And how much energy would that require, and where does it come from?

These gravity particles of course are not known currently, but if they are hypothesized, this issue might not exist: a proton you mentioned not only emits particles to interact with everything else, but also absorbs particles emitted by everything else which interacts with it.

[Mordred]

It also describes the mechanism all particles will choose the path of least action. You do not need gravitons to mediate spacetime. Spacetime curvature is the only mechanism you require which requires the mass term as mentioned even massless particles can contribute to curvature.

Try this for a thought experiment  take a uniform distribution of mass where every point has the same mass. Then apply Newtons Shell theorem using any random point as the designated centre of mass. In this case you would experience no gravity at any location. You need regions of non uniform mass distribution.

Edited May 8, 2023 by Mordred

[mistermack]

4 minutes ago, Genady said:

but also absorbs particles emitted by everything else which interacts with it.

Which is every particle and every bit of energy in the universe, isn't it? 

6 minutes ago, Mordred said:

It also describes the mechanism all particles will choose the path of least action. You do not need gravitons to mediate spacetime.

But then there's a mechanism in which the path of least action is shaped, that needs explaining.